This invention relates to a switching valve device in an air suspension system for automobiles provided between a plurality of air chambers sectioned with partition walls or diaphragms to freely adjust the amount of air flowing between respective air chambers.
There has been already known in such vehicles as automobiles an air suspension system wherein air chambers are provided above a shock absorber disposed between the body and axle of such a vehicle as an automobile to make or attain a spring action with high pressure air enclosed in the air chambers.
An air chamber in an air suspension system in sectioned usually into a plurality of, for example, two air chambers, and the respective air chambers are connected or disconnected with each other to vary the so-called air spring constant and to improve the riding comfort of the vehicle equipped with this air suspension system. A air suspension conventional system as is shown, for example, in hereinafter described FIGS. 6 to 8, is suggested as an air suspension system therefor.
That is to say, as shown in FIG. 6 suspension system has two air chambers A and B sectioned with a diaphragm C, housing D and partition wall E between the upper end part of a cylinder 1 and the upper end part of a piston rod 2 extending out of and into the cylinder 1 and is provided with a switching valve 4 in a path 3 connecting the two air chambers A and B with each other. The switching valve 4 is operated to be switched by an actuator 5 provided at the upper end of the piston rod 2 to connect the above mentioned air chambers A and B with each other to make or attain a so-called soft air spring constant or to throttle or disconnect the above mentioned air chambers A and B with respect to each other to make or attain a so-called hard air spring constant by utilizing only one main air chamber A.
As shown in FIGS. 7 and 8, a housing 8 is held through a rubber bush 7 within a casing 6 formed to enclose the upper end part of the piston rod 2 and the above mentioned switching valve 4 is formed of a rotary valve contained and fitted rotatably within this housing 8. The above mentioned path 3 consists of an air chamber B side path 3a and an air chamber A side path 3b. One path 3a is formed of a port 6a of the casing 6, port 7a of the rubber bush 7 and port 8a of the housing 8. The other path 3b is formed of an opening Ea of the partition wall E, opening 6b of the casing 6 and lower chamber 6c of the casing 6. The path 3a and path 3b are connected with each other through a path 4a provided in the rotary valve 4 so that, whenthe rotary valve 4 is rotated to displace the position of the path 4a, the paths 3a and 3b will be throttled or disconnected and both air chambers A and B will be disconnected with respect to each other.
Therefore, when the switching valve 4 which is the rotary valve is operated to be switched, any desired air spring constnt will be obtained and the riding comfort, for example, of a vehicle or the like will be improved.
However, when both air chambers A and B are connected with each other, if the air suspension system operates to extend, an air flow will be produced between the air chambers A and B through the above mentioned path, 3 and the air flow through the above mentioned path 3 will be in a so-called high speed state. When particularly the air suspension system operates to extend to produce such air flows, as are indicated by the arrows a and b in FIG. 8, toward the air chamber A from the air chamber B, through both paths 8a, 8a formed as opposed to each other to secure, flow path areas and the paths 4a, 4a of the switching valve, disadvantageously the air flows from both directions will collide with each other in the path 3b within the switching valve 4. The air flows will be turbulent, and a sound will be generated by the turbulence.
Also, at the same above mentioned time, the air chamber B side will be higher in pressure than the air chamber A side, and therefore the high pressure air flowing into the path 3b within the switching valve 4 through the paths 4a,4a of the switching valve 4 will be quickly made low in pressure and in turn a so-called swish sound will be disadvantageously generated.